Center locating device



/7 7- TERA/5 5 May 11, 1954 H. F. WAHL CENTER LOCATING DEVICE Filed Aug. 25, 1952 M M WI/fi z/2 p Z o 4 l. Y 2 2 a 6 5 1 0 g v0 6 not commonly used in the trades.

UNITED STATES PATENT OFFICE CENTER LOCATIN G DEVICE Harold F. Wahl, Portland, Oreg. Application August 25, 1952, Serial No. 306,220

17 Claims. 1

This invention relates to a geometrical instrument for mechanically locating the centers of objects having shapes which are either circular or in the form of a regular polygon.

The numerous devices heretofore proposed for this purpose are generally unsatisfactory and are Most of them require the reading of scales and the making of calibrated adjustments in various joints of a more or less complicated linkage or the like. Such devices, besides being quite susceptible to human and mechanical error, and tedious to use, are intricate and expensive to manufacture, having numerous movingparts and pivotal connections which are subject to looseness and wear. The known devices which are more practical from this standpoint are usually limited as to the shapes and sizes of'work pieces they will accommodate.

Objects of the present invention are, therefore,

to provide a'center locator of general application to a wider range of sizes and shapes; to provide a center locator which is entirely mechanical and automatic in its action and does not rely upon scales and visual measurements; to provide a device which is relatively simple and inexpensive to manufacture, and which is at the same time durable and reliable in operation; to provide a device of few moving parts with a minimum of joints and connections subject to wear and looseness; and, in general, to provide an improved and more practical instrument which will satisfy the needs of the trades better than the known devices.

By the novel application of certain geometrical principles, the present device operates automatically by the simple adjustment of a single movable stop member to contact a surface of the work piece Without the necessity for reading scales, taking measurements or making calibrated adjustments. The device in its simplest form will accomodate circular shapes and all regular polygons having a number of sides which is a multiple of four. The principles of the invention are also applicable to other regular polygons, and a form of the device is illustrated which Will accommodate a hexagonal shape. The tool may be made in various sizesto find the centers of a wide variety of work pieces such as pistons,

wood working stock, bar stock of all the standard shapes and sizes, large cylindrical tank ends, peeler logs to be mounted in a veneer lathe, and for otherpurposes. The principles of the invention may he applied to both outside and inside calipering and to the location of the centers of geometrical areason maps, charts, photographs and the like. Obviously, the details of construction will vary in such widely different applications, but the embodiments shown on the accompanying drawings will serve to illustrate the principles of the invention'so that others skilled in the art may apply these principles in other fields of use. It is, therefore, to be understood that the accompanying drawings are to be considered merely as illustrative and not limiting the invention.

In the drawings:

Figure 1 is a plan view of a device embodying the principles of the invention for use primarily with objects having a shape which is circular, square or octagonal;

Figure 2 is a sectional view taken on the line 22 of Figure 1;

Figure 3 is a sectional view taken on the line 3-3 of Figure 1;

Figure 4 is a sectional view taken on the line l-4 of Figure 1;

Figure 5 is a fragmentary view of a modification adapted to accommodate hexagonal shapes;

Figure 6 is a diagram illustrating the geometrical principles of the present invention which are involved in locating the center of a circle;

Figure '7 is a diagram illustratingthe principles involved in finding the center of a square or octagon; and

Figure 8 is a diagram illustrating the principles involved in finding the center of a hexagon.

Circular and square shapes Referring first to Figure 6, the rectangular coordinate axes OX and CY form a right angle at the point of intersection O. Circles of different sizes may be drawn tangent to these lines, as shown, having centers at P1, P2, .P3. The points of .tangency with the line OX are designated at a, b, c, the vertical lines a, m, b, in, 0, or being .diametersof the respective circles. Horizontal lines a1, oz, b1, b2, and c1, 02 are perpendicular to OY and tangent to the respective circles at :11, b1, 01. By geometry, the centers P1, P2,.P3 fall on a straight line CW, and thepoints m, b1, 01 fall on a straight line OZ. Also by geometry, a, a1 equals 2m, :12; b, in equals 2121, b2; and 0, c1 equals 201, 02. Hence, the tangent of the angle A equals ,.making the angle A equal to 26.56505+ and the tangent of the angle B equals 2.0, making ,the angle B equal to 63.43495. Agaimby geometry, the angle XOW equals 45? and its tangent equals 1.0. The angle between OW and OZ is, therefore, 18.43495.

Thus, the rule may be formulated that the centers P1, P2, P3 lie at the points where perpendiculars dropped from points m, b1, 01 intersect the 45 line OW, or, more generally stated, perpendiculars dropped from points of intersection of the 63.43495 line OZ with the circles define vertical diameters which are bisected by the 45 line OW to locate the respective centers.

In Fig. '7, the three squares have centers at P4, P5 and P6 lying on the 45 line OW. The points d, e and f are located at the midpoints of the bottom sides of these squares, and the perpendiculars d, (11, a, el, 1, ii are erected. In this case, the lines d1, d2, 61, e2, and f1, f2 coincide with the top sides of the squares. Just as in Figure 6, the tangent of the angle A equals giving the same value of 26.56505+ for this angle. Again, also, the centers P4, P5, and P6 lie on points where perpendiculars dropped from the points d1, e1, f1 intersect the 45 line OW.

The foregoing geometrical principles are embodied in a practical mechanical device in Figures 1 and 2. A flat plate Ill having a square corner at O is equipped with a horizontal bottom fence I! and a vertical side fence 12 to establish the coordinate axes OX and OY in Figures 4 and 5. A 15 stepped guide slot I3 establishes the locus of points on the line OW, and a second guide slot M at an angle of 26.56505 from the side fence l2 establishes the locus of points on the line OZ.

The extended center lines of both slots intersect at the point 0.

When a circular or square shaped object is placed in contact with the fences l! and I2, the points a1, b1, 01, or d1, 61, ii, are located by a sliding trammel stop l5 mounted for travel in the slot Hi. The work contacting head of trammel stop 15 overlies the plate It) on opposite sides of the slot l4 and is formed with an angular portion presenting a corner having a blunt knife edge IE to contact a thick work piece in line contact, as viewed in Figure 2, and in substantially point contact when the third dimension of the work piece is small, as illustrated in Figure 1. The trammel stop 15 also includes a sliding key portion I! which is elongated in the direction of slot l4 and engages the slot in a good sliding fit to prevent rotation of the trammel stop in the slot.

A trammel bar is secured to the trammel stop 15 in a fixed position so that the trammel bar will be maintained perpendicular to the bottom fence H, the parts being held in assembled relation in the slot I4 to provide the desired degree of sliding friction by means of clamp nut 2|. The trammel bar 20 is equipped with a vertical guide slot 24.

A center locating element in the form of a sliding pilot has a portion 26 engaging and guided by the slot 13, and another portion 2'! engaging and guided by the trammel guide slot 24. The sliding pilot is preferably equipped with a pilot hole 28 to receive a center drill, center punch or other marking device. The sliding pilot is held in assembled relation with the plate l5 and trammel bar 20 by clamp nuts 29 which act against a sliding bushing 36 to maintain the proper sliding friction. Suitable auxiliary locking devices shown in the art may be employed in conjunction with the clamp nuts 2| and 29, if desired, to facilitate adjustment without allowing objectionable looseness of the parts. Pilot hole 28 is located at the intersection of the center lines of slots !3 and 24 and contact edge I 6 is located at the intersection of the center lines of slots I4 and 24.

From the foregoing geometrical analysis in connection with Figure 6, it will be apparent that the slot [4 will guide the trammel stop edge 16 into contact with the top side of a circular work piece at the precise upper end of its vertical diameter corresponding to the points on, hi, or in Figure 6. The cooperating guide means on the center locating element 25 and trammel plate 24 positions the pilot hole 28 on a vertical line beneath the edge [6, and the pilot guide slot l3 serves to bisect the lines a, a1, 1), b1, 0, c1 to locate the centers P1, P2, P3. When a center punch is used to mark the center, the pilot hole 28 prevents drifting of the punch point on the end grain of wood or other irregular surface. The clamping action of trammel stop l5 against the work piece, by the tightening of clamp nuts 2i and 29 when desired, tends to hold the work piece securely, which is of advantage in the case of small work pieces.

In a similar manner, the slot !4 guides the trammel edge 16 down into contact with the precise center of the top edge of a square object, as indicated by the points (11, e1, ii in Figure '7, and the vertical trammel bar 20 and 45 slot l3 cooperatively guide the center locating element 25 to position the pilot hole 28 to bisect the vertical lines (1, d1, e, 61, 1, f1 for locating the centers P4, P5, P6. It is readily apparent that the device of Figure 1 will operate in the same manner to locate the centers of regular polygons having eight, twelve, sixteen or more sides in any number even- 1y divisible by four.

Hexagonal shape In Figure 8, a circle of unit radius is drawn about the center P9 tangent to the line OX at i and tangent to the line OY at 9', and the lines 0W and OZ drawn as in Figure l, the point 2' corresponding to the point 0 and the point i1 corresponding to the point c1. circumscribed about this circle is drawn a hexagon, also having its geometrical center at P9. The radius P97 extended intersects the vertex is of the hexagon. The radius P91 is drawn making a right triangle P9761, wherein the angle kPsZ is 30". Hence, Pol/P970 equals cosine 30 equals 0.86602540, yielding the value of l.l547+ for the length of line P9k, and 0.l547+ for the length of line 770. Therefore, the tangent of angle C equals giving the value to the angle C of 8.79397+.

By the well known theorum establishing the proportionality of the corresponding sides of similar triangles, it will be apparent that the corresponding vertices of larger and smaller hexagons will also lie upon the line OV, as illustrated, the entire angle XOV being equal to 98.79397+. In this case, it is convenient to refer all the angles to the OX axis, it being noted that the lines OW, OZ, CY and 0V all pass through the point 0. Thus, using the OX axis as a reference or base line, the angle XOW equals 45, the angle XOZ equals 63.43495+, the angle XOY equals and the angle XOV equals 98.79397+.

Further, considering the OX line as the base or reference line, the tangent of the angle XOW equals 1, whereas the tangent of the angle XOZ equals 2, whereby perpendiculars dropped from the points g1, hi, ii are bisected by the line OW to locate the centers of the respective hexagons at P7, P8, and P9. Again, by geometry, it will be apparent that the line OZ passes through the points 91, hi, just as it passes through the point of the fence member .of 98.79397+ cating the centers of hexagonal work pieces. The fence I20: may, of course, be mounted perma- .in Figure to locate ii, the inscribed-circles for the smaller hexagons eing omitted to avoidconfusion in the diagram.

Itis further apparent that if circles wereinscribed in the small hexagons, the points or and hl would correspond to an and b1 inFigure 6.

Applying the foregoing geometrical develop- -ment to a practical center locating device, Figa bottom fence .plate I 011 is equipped with a trammel stop it,

trammel bar 20, and center locating element 25,

intersection of the center lines of guide slots 13 and I4 extended. The work engaging surfaces of the fences II and in also intersect at this point.

The plate Illa is provided with a hole 4: to receive a pin or screw dowel 32 in the upper end to secure the fence at an angle of 90 to the bottom fence H, as indicated in broken lines. In this position of the fence I2a, the device in Figure 5 functions the same as the "device in Figure 1 to locate the centers of round,

square and octagonal Work pieces.

When thefence In is shifted to its full line position, the pin 42 may be inserted into a second hole, not shown, to secure'the fence at an angle from the bottom fence H for nently in its full line position, if desired.

Thus, the objects of the invention are attained in a'relatively simple, inexpensive and rugged device which is easy 'to manipulate and use with a high degree of accuracy. When constructed as shown in Figures 1 and 5, the device will accommodate work pieces of very small size, while, on the otherhand, it will be apparent to persons skilled in the art that the principles of the invention may b embodied in a device of sufiicient size to locate the centers of large logs and circular'tank ends and the like.

It will also be apparent to persons skilled in the art that the geometrical development illustrated in Figure 8 may be applied and extended to determine the value of the angle offenc I; the centers of objects or areas of other shapes, and it is within the scope of the invention to provide additional holes in the plate lila, or other equivalent securing means, to position the fence i2a at any such predetermined angle.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

tersection of said reference lines at an angle to one of said reference lines having a tangent function of 2.0, a movable center locating element, guide means forsaid center locating element extending in astraight linefrom said point of in- .tersection atan angle tosaid onereference line extending in a straight .having a tangent function of 1.0, and cooperatving guide means on'said trammel member and center locating element to position the latter .always on a perpendicular line between said trammel member and. said one reference line.

2. A device for locating the centers of circular and regular polygonal objects comprising means to contact the perimeter of th object at two points having a central angle spacing of in angel of 63.43495 to said one fence member to contact the periphery of the object, and means 5. A center locator for objects of circular and regular polygonal shapes comprising a pair of straight fence members disposed at a predetermined angle to each other to contact two points on the periphery of the object having a central angle spacing of 90 in the case of a circular object, a movable trammel stop constrained to travel in a straight line at an angle of 63.43495- to one of said fence members to contact a third point on the periphery of the object, a movable center locating element constrained to travel in a straight lin at an angle of 45 to said one fence member, and cooperating means on said trammel stop and center locating element to position the latter always on a line from said trammel stop extending perpendicular to said one fence.

6..A center locator for objects of circular and regular polygonal shapes comprising a, \pair of straight fence members disposed at a predetermined angle to each other to contact the periphery of the object, a movable trammel stop to contact the periphery of the object, said trammel stop having a locus in a straight line extending from the point of intersection of said fence lines at an angle of 63.43495- to one of said fence members, a movable center locating element having a locus in a straight line extending from said point of intersection at an angle of 45 to said one fence member, and cooperating guide means on said trammel stop and center locating element to position the latter always on a perpendicular line between said trammel stop and said one fence member.

'I. A center locator for objects of circular and regular polygonal shapes comprising a pair of straight fence members disposed at a predetermined angle to each other to contact the periphery of the object, a movable trammel stop to contact the periphery of the object, guide means for said trammel stop extending in a straight line from the point of intersection of said fence lines at an angle of 63.43495- to one of said fence members, a movable center locating element, guide means for said center locating element extending in a straight line from said point of intersection at an angle of 45 to said one fence member, and cooperating guide means on said trammel stop and center locating element to position the latter always on a perpendicular line between said trammel stop and said one fence member.

3. A center locator for objects of circular shape and regular polygons having a number of sides equal to a multiple of four comprising the structure defined in claim '1 wherein the two fence members are disposed at an angle of 90 to each other.

9. A center locator for objects of hexagonal shape comprising the structure defined in claim '7 wherein the two fence members are disposed at an angle of 98.7939'7+ to each other.

10. A center locator as defied in claim '7 having means to secure the other fence member at different predetermined angles relative to said one fence member.

11. A center locator as which at least one of defined in claim '7 in said fence members is pivotally mounted on the locator, and fastening means to secure said pivotally mounted fence member in at least one other angular relation different from said first predetermined angular relation between said fence members.

12. A center locator for objects of circular and regular polygonal shapes comprising a plate having a pair of straight fence members disposed at a predetermined angle to each other to contact the periphery of the object, a trammel guide slot in said plate extending on a line from the point of intersection of said fence lines at an angle of 63.43495 to one of said fence members, a sliding trammel stop movable in said slot to contact the periphery of the object, a slot in said plate said point of intersection at an angle of 45 to said one fence member, a center locating element movable in said last mentioned slot, and cooperating guide means on said trammel stop and center locating element to position the latter always on a perpendicular line between said trammel stop and said one fence.

13. A device for locating the center points of circles and regular polygons comprising means defining a pair of intersecting straight reference extending in a straight line from lines disposed at degrees with respect to each other, a movable trammel member, guide means for said trammel member operably effective along a straight line intersecting said reference lines at the point of intersection of such lines with said line extending at an angle with respect to one of said reference lines, said angle having a tangent function of 2.0, a movable center locating element, guide means for said center locating element extending along a straight line from the point of intersection of said reference lines and at an angle with respect to the aforesaid one reference line, said angle having a tangent function of 1.0, and cooperative orientation means operatively connecting said trammel member with said center locating element and functioning to maintain said member and element in positions perpendicularly related with respect to said one reference line aforesaid.

14. A center locator for circular and regular polygonal objects comprising a base for the perpendicular support of one of said objects, fence members carried by said base and disposed at predetermined angular relation with respect to each other and for peripheral side contact with said perpendicularly supported object, a center locating element mounted upon said base and arranged for straight line travel at an angle of 45 degrees with respect to one of said fence members and into a position adjacent one end of said object, a trammel stop mounted upon said base and arranged for straight line travel at an angle of 63.43495 degrees with respect to said one fence member and for peripheral side contact with said object, and orientation means connecting and maintaining said center locating element and said trammel stop in aligned positions along a line disposed perpendicular with respect to said one fence member.

15. A center locator for circular and regular polygonal objects comprising a base for the perpendicular support of one of said objects. fence members carried by said base and disposed at predetermined angular relation with respect to each other and for peripheral side contact with said perpendicularly supported object, a center locating element mounted upon said base and arranged for straight line travel along a path following a line bisecting the angle formed between said fence members and into a position adjacent one end of said object, a trammel stop mounted upon said base and arranged for travel along a straight line radiating from the juncture of said fence members and disposed at a predetermined angular relation with respect to said straight line path of said center locating element and for peripheral side contact with said object, and orientation means connecting and maintaining said locating element and said trammel stop in aligned positions upon a line disposed in a given angular relation with respect to one of said fence members.

A center locator for objects having a circular or regular polygonal end comprising a flat base adapted to contact said end of the object, a pair of fence members carried by said base and disposed in predetermined angular relation with respect to each other for peripheral side contact with said object adjacent said end, a movable center locating element mounted upon said base and constrained to travel in a path along a. straight line bisecting the angle formed between said fence members and into a position adjacent said end of the object, a movable trammel stop mounted upon said base and constrained to travel 2,677,893 10 in a path along a straight line radiating from and constrained to travel in a path along a the juncture of said fence members and disposed straight line bisecting the angle formed between in a predetermined angular position with respect said reference lines, a movable trammel stop element and for peripheral side contact with said 5 to travel in a path along a straight line radiatobject adjacent said end, and orientation means ing from the juncture of said reference lines and connecting and maintaining said locating eledisposed in a predetermined angular position ment and said trammel stop in aligned positions with respect to said straight line of said upon a line disposed in a predetermined angular e ter lfi at n lement, and i t relation with respect to one of said fence mem- 10 gag n Sa d base and Conneeting and mainbers. taining said locating element and trammel mem- 1'7. In a device for locating the centers of cirher in aligned positions upon a line disposed cles and regular polygons, a fiat base member, in predetermined angular relation to one of said means on said base member defining pair of reference lines. straight reference lines disposed at a predetero mined angle to each other, a movable center 10- No references cited eating element mounted on said base member 

